Soft Magnetic Iron Alloy Sheet Balancing High Bs and Low Iron Loss
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Solution Overview
Problem
Existing soft magnetic materials face challenges in achieving high saturation magnetic flux density (Bs) and low iron loss (Pi) while maintaining cost-effectiveness, as materials like electromagnetic pure iron sheets have high Pi and high Co-based materials like Permendur are costly and difficult to process.
Innovation Solution
A soft magnetic iron alloy sheet with a composition of 1-30% Co, 0.5-10% N, and 0-1.2% V, featuring a ferrite phase and iron nitride phases with a tetragonal structure, is manufactured by applying a tensile strain within a specific range and forming an electrical insulating film to maintain tensile strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If electromagnetic pure iron sheet is used, then saturation magnetic flux density is high, but iron loss is high
Solution Approach 1:
The invention changes the chemical composition parameters by adding specific amounts of Co (1-30 mass%), N (0.05-10 mass%), and V (0-1.2 mass%) to the pure iron base, transforming it into a soft magnetic iron alloy sheet. This parameter change resolves the contradiction by achieving Bs ≥ 2.20 T while maintaining Pi ≤ 25 W/kg at 1.0 T and 400 Hz, as the alloying elements modify the magnetic properties and reduce eddy current losses through increased electrical resistance.
Solution Approach 2:
The invention creates a composite material system by combining multiple elements (Fe-Co-N-V alloy) with specific phases (ferrite phase as primary phase, iron nitride phases including tetragonal structure phases). This composite approach allows simultaneous achievement of high saturation magnetic flux density and low iron loss by leveraging the complementary properties of different phases and elements.
2Quantity of substance
If Co-based materials like Permendur are used, then saturation magnetic flux density is high, but manufacturing cost is high and processing difficulty increases
Solution Approach 1:
The invention optimizes the Co content parameter within a specific range (1-30 mass%) rather than using high-Co formulations like Permendur. This parameter optimization achieves Bs ≥ 2.20 T while significantly reducing material cost and improving processability compared to conventional high-Co alloys, as demonstrated by the successful manufacturing of sheets with controlled phase composition and microstructure.
Solution Approach 2:
The invention applies local quality control by specifying particular phase compositions and distributions within the alloy (ferrite phase as primary phase with specific iron nitride phases). This allows different regions or aspects of the material to have optimized properties: high Bs from the alloy composition, low Pi from the phase structure, and improved manufacturability from the controlled microstructure, resolving the contradiction between performance and ease of manufacture.
3Strength
If Si is added to electromagnetic steel sheet, then strength increases and iron loss decreases, but saturation magnetic flux density decreases
Solution Approach 1:
The invention uses a composite alloying strategy combining Co, N, and V elements instead of relying on Si addition. This composite approach achieves both high strength and high saturation magnetic flux density simultaneously, as the Co-N-V system provides both mechanical strengthening mechanisms and enhanced magnetic properties without the Bs reduction penalty associated with Si-containing steels.
Solution Approach 2:
The invention changes the alloying parameter set by selecting Co, N, and V as primary alloying elements rather than Si. This parameter substitution resolves the contradiction because the Co-N-V system provides both strength enhancement (through precipitation hardening and solid solution strengthening) and magnetic property improvement (through phase composition control), whereas Si addition inherently reduces Bs despite improving strength and reducing losses.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The alloy sheet achieves a saturation magnetic flux density above 2.20 T and iron loss below 25 W/kg, reducing costs compared to Permendur and improving processing efficiency.
Implementation Method 1
0.5 at % or more and 10 at % or less of N (nitrogen) is dissolved, an iron nitride phase... is formed
Implementation Method 2
a soft magnetic iron alloy sheet including... iron nitride phase (FesN phase and/or Fe16N2 phase) having a tetragonal structure
Implementation Method 3
a tensile strain is generated in a range of 10% or more and 110% or less of a tensile elastic limit strain along an in-plane direction... coercive force Hc is low
Implementation Method 4
an increase in electrical resistance or a reduction in thickness is effective for reducing the eddy current loss
Data Source
AI summary
A soft magnetic iron alloy sheet having higher Bs and lower Pi than an electromagnetic pure iron sheet is capable of further reducing the cost as compared to Permendur. A method of manufacturing the soft magnetic iron alloy sheet, and an iron core and a rotating electric machine including the soft magnetic iron alloy sheet are provided. The soft magnetic iron alloy sheet includes 1 to 30 at % of Co, 0.5 to 10 at % of N, 0 to 1.2 at % of V, and a remainder consisting of Fe and impurities. The soft magnetic iron alloy sheet includes ferrite phase as a primary phase and iron nitride phase having a tetragonal structure. A tensile strain is generated in a range of 10% or more and 110% or less of a tensile elastic limit strain along an in-plane direction of the soft magnetic iron alloy sheet.